I just received mine today (8/31/2013) and put it on my week old 2013 MacBook Air 13". I can confirm that the case does NOT cover the 2nd microphone port, but comes to about 1/16" of it.

I assume that the manufacturer is no longer making the older cases and has switched to the new model to accommodate the new MacBook Air dual mics.

It's 2 piece, top and bottom and clips around the edges. It has a rubbery slick feel, not very grippy, almost feels a bit more slippery than the bare aluminum of the Mac Air, but i feel a lot safer about not scratching my shiny new MacBook Air by accident, and that was my goal.

Great simple and practical product.

The instructions say to take it off each month to clean underneath, but I doubt the tiny tabs holding it to the Air will survive repeated removal and reattachment....

the guy saying it doesn't cover the mic is TOTALLY WRONG. i was wondering why i was struggling with mine and found that it is covered by about a millimeter and while that isn't much it's more than enough.